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A merger between SSE Retail and nPower has been given the go-ahead by the Competition and Markets Authority.
Anne Lambert, chairwoman of the inquiry group examining the deal, says: "With many energy companies out there, people switching away from expensive standard variable tariffs (SVT) will still have plenty of choice when they shop around after this merger.
"But we know that the energy market still isn't working well for many people who don't switch, so we looked carefully at how the merger would affect SVT prices.
"Following a thorough investigation and consultation, we are confident that SSE and Npower are not close rivals for these customers and so the deal will not change how they set SVT prices."
The Competition and Markets Authority has no concerns about the Scottish energy firm SSE's proposed merger with Npower.
Anne Lambert of the CMA explains the competition watchdog's reasoning:
"It is vital that householders have a range of energy suppliers to choose from so they can find the best deal for them. With more than 70 energy companies out there, we have found that there is plenty of choice when people shop around."
BBC Business News
Gas and electricity supplier Npower is raising energy bills by an average of £64 a year for a million customers.
The average 5.3% dual fuel price hike comes into effect on 17 June and follows earlier rises announced last month by its "Big Six" rivals.
British Gas is increasing prices by 5.5% from 29 May, while EDF is raising electricity prices by 2.7%.
The company which has it's UK base in Worcester blamed increases in policy and wholesale energy costs for the increase.